Dietary P regulates phosphate transporter expression, phosphatase activity, and effluent P partitioning in trout culture
Abstract
Phosphate utilization by fish is an important issue because of its critical roles in fish growth and aquatic environmental pollution. High dietary phosphorus (P) levels typically decrease the efficiency of P utilization, thereby increasing the amount of P excreted as metabolic waste in effluents emanating from rainbow trout aquaculture. In mammals, vitamin D3 is a known regulator of P utilization but in fish, its regulatory role is unclear. Moreover, the effects of dietary P and vitamin D3 on expression of enzymatic and transport systems potentially involved in phosphate utilization are little known. We therefore monitored production of effluent P, levels of plasma vitamin D3 metabolites, as well as expression of phosphatases and the sodium phosphate cotransporter (NaPi2) in trout fed semipu diets that varied in dietary P and vitamin D3 levels. Mean soluble P concentrations varied markedly with dietary P but not with vitamin D3, and constituted 40–70% of total effluent P production by trout. Particulate P concentrations accounted for 25–50% of effluent P production, but did not vary with dietary P or vitamin D3. P in settleable wastes accounted for <10% of effluent P. The stronger effect of dietary P on effluent P levels is paralleled by its striking effects on phosphatases and NaPi2. The mRNA abundance of the intestinal and renal sodium phosphate transporters increased in fish fed low dietary P; vitamin D3 had no effect. Low-P diets reduced plasma phosphate concentrations. Intracellular phytase activity increased but brushborder alkaline phosphatase activity decreased in the intestine, pyloric caeca, and gills of trout fed diets containing low dietary P. Vitamin D3 had no effect on enzyme activities. Moreover, plasma concentrations of 25-hydroxyvitamin D3 and of 1,25-dihydroxyvitamin D3 were unaffected by dietary P and vitamin D3 levels. The major regulator of P metabolism, and ultimately of levels of P in the effluent from trout culture, is dietary P.
Citation
Coloso, R. M., King, K., Fletcher, J. W., Weis, P., Werner, A., & Ferraris, R. P. (2003). Dietary P regulates phosphate transporter expression, phosphatase activity, and effluent P partitioning in trout culture.Publisher
Springer VerlagSubject
Acknowledgment/Sponsorship
This project was supported by the Northeastern Regional Aquaculture Center (NRAC)-USDA Grant no. 94-38500-0044) and USDA-CSREES-NRI Grant no. 2001-35102-09881. R. Ferraris’ laboratory also received support from NSF-IBN9985805. We thank S. Basantes, A. Garcia, J. Choi, and F. Liu for help in the chemical analyses of the water, fecal, and carcass samples, Dr. M. Subramanyam for his suggestions on the formulation of the semi-purified diets, P. Farrell for the expert technical assistance during field sampling, F. Jarder for the proximate analyses of the diets, K. Powers of Pequest Fish Hatchery for the fish and Dr. A. Ritter for statistical advice.
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L-ascorbyl-2-phosphate Mg as vitamin C source for juvenile Penaeus monodon
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Article
L-ascorbyl-2-phosphate Mg as source of vitamin C for juvenile Penaeus monodon
-The Israeli Journal of Aquaculture-Bamidgeh , 1994 - Society of Israeli Aquaculture and Marine BiotechnologyPhosphated ascorbic acid (MAP), a stable vitamin C derivative, was used in practical diets for Penaeus monodon (wet weight, 126-254 mg) as a source of vitamin C. In Experiment I, the levels were from 0 to 1,500 ppm MAP. No significant differences in weight gain, SGR, survival and FCR were observed among treatment means after 92 days of feeding but the lowest values were obtained in the group fed without the MAP dietary supplement. At the start of the experiment shrimps were infected with monodon baculovirus (MBV). However, the histological structure of the hepatopancreas showed improvement in animals fed diets containing 100 ppm MAP and above, after 92 days. In Experiment II, shrimps were given different MAP levels (0 to 8,000 ppm) for 81 days. The FCR and survival of shrimps in MAP supplemented diets were significantly higher than those without MAP. In both experiments, shrimps without dietary MAP were weak and developed blackened subcuticular tissues, a symptom of vitamin C deficiency. MAP was utilized by P. monodon as a source of vitamin C. An adequate level in a practical diet would be 100 to 200 ppm MAP, equivalent to 50 to 100 ppm ascorbic acid.
